Senior Backend Python Engineer

Are you looking to be key technical contributor to a fast-growing AI platform that's redefining how the world builds intelligent systems? Do you want the chance to participate in the open-source AI movement? Are you passionate about building the future of AI alongside a world-class machine learning (ML) team, within a remote-first culture that values ownership and initiative? Then Flower Labs is the place for you.

At Flower Labs, we're looking who wants to use their talents to architect, design and implement tools and platforms that will be used by millions of people world-wide (including scientists, engineers, students) and have a profound impact on the future of various societally important domains such as medicine, and more. As Senior Backend Python Engineer, you'll play a critical role in building critical pieces of the #1 open-source solution for federated and decentralized AI — already trusted by Fortune 500 companies and a 6000+ developer community.

Flower Labs is the world-class AI startup behind Flower, the most popular open-source framework in the world for training AI on distributed data and compute resources using federated learning. Trusted by industry leaders such as Mozilla, Owkin, Banking Circle, JP Morgan, Samsung, Temenos and Bosch, Flower enables organizations to improve their AI models on sensitive data that remains securely distributed across organizational silos or user devices. In a world where most AI relies on centralized public datasets — just a fraction of the data available — we believe unlocking access to (orders of magnitude more) private data will drive the next breakthroughs in artificial intelligence.

Flower Labs is a Y Combinator (YCW23) graduate and backed by top-tier investors and renowned angels, including Felicis, First Spark Ventures, Mozilla Ventures, Hugging Face CEO Clem Delangue, GitHub Co-Founder Scott Chacon, Factorial Capital, Betaworks, and Pioneer Fund. Together, we are redefining how AI is built, deployed, and scaled.

As a Senior Backend Python Engineer, you will work across our entire stack. This includes the Flower open-source project, our internal monorepo, and high-impact user projects. We are looking for people able to assume technical leadership roles, and work with others to build the critical components that will advance the Flower ecosystem forward. For this position we are currently hiring in the UK and Germany but are open other for Europe-based applicants to better align with the current time zones of most of the team.

System Design & Architecture

• Design, implement, and evolve distributed systems and backend services supporting Flower's open-source and enterprise platforms.
• Define and maintain architectural standards and best practices to ensure reliability, scalability, and performance.
• Contribute to shaping the long-term technical roadmap across multiple projects and teams.
• Collaborate with frontend, research, and infrastructure teams to deliver cohesive and efficient solutions.

Core Development & Execution

• Write clean, maintainable, and well-tested Python code with a focus on quality and performance.
• Lead development of new backend features, APIs, and integrations used by thousands of developers.
• Improve the stability and observability of our services through testing, monitoring, and continuous delivery.
• Drive code reviews, mentoring, and knowledge sharing within the team.

Open Source & Community

• Contribute directly to the Flower open-source project and help grow its ecosystem.
• Review and guide community contributions to maintain high standards and consistent design.
• Support open collaboration through documentation, issue triage, and RFC discussions.
• Represent Flower in community events, conferences, and developer meetups.

Performance & Reliability

• Profile, optimize, and refactor critical code paths to improve performance under real-world workloads.
• Design scalable storage, messaging, and computation solutions for federated and distributed systems.
• Ensure system reliability and resilience through automation, CI/CD, and observability practices.

Security & Data Integrity

• Implement secure design patterns for communication, authentication, and data exchange.
• Contribute to internal security reviews, audits, and key management improvements.
• Promote best practices for privacy-preserving machine learning and data handling.

You can expect a mission-driven, collaborative, fast-paced start-up environment with experts in their respective fields. Everyone learns something new every day. Since we are still in the early phases of our mission (i.e., taking decentralized AI mainstream), you will have many opportunities to contribute ideas, be heard, and influence the direction of the company across the board. On a personal level, we value collaboration over competition. We're working in a highly competitive field and believe we can only win by collaborating and acting as one team.

We're looking for a strategic and hands-on backend engineer who's passionate about building exceptional systems, contributing to open-source ecosystems, and shaping the future of AI through world-class engineering.

• Independently author, test, ship, and monitor features used by thousands of users
• Preference for async remote work
• Exceptional Python skills, willingness to work with other languages
• Familiarity with common tools (Linux command line, git, Docker, …)
• Openness to adopting new tooling
• Solid understanding of distributed systems
• Strong written English
• Experience with gRPC, REST, and general API design
• Open, honest and transparent communication skills

• An understanding of machine learning
• Hands-on experience in PyTorch and multi-GPU environments